Stalling at idle in gear

Most the time it stalls as I am coming to a stop. Doesn't feel like it's pushing me forward at all. I had the revs up thinking that it was too low, but left it alone after fixing some fueling issues. It stumbles a little in reverse, which is also why I think the converter may be an issue. It stays running if I shove it into neutral once it starts sputtering.
I let the guy who built the trans put the lockup in thinking it'd help with fuel economy, but that doesn't mean crap to me if I can barely drive the thing. If the lockup isn't releasing then it's putting too much of a load on the engine at idle and making it stall. I don't want that part of it haha.